Enhancement: Advanced Live Channels listing filter (group filter, AND/OR/NOT syntax)

[LagaV]

Is your feature request related to a problem? Please describe.
Selecting and filtering channels quickly becomes difficult when there are many similar entries, or when grouping/channel tags are heavily used. Currently, the channel search is a plain substring match and does not allow users to:

• Filter by group via the search UI without scrolling/group switching
• Chain multiple conditions
• Exclude (NOT) or combine (AND/OR) terms

Describe the solution you'd like

• Add an optional group-level dropdown filter or search input, making it easy to restrict the shown channels to only a selected group (or groups).
• Extend the search filter for the Live Channels list to support a simple query syntax:
  • Allow filters like group:{search string} to filter by group name explicitly within the main search bar
  • Multiple search entries (space- or comma-separated) are treated as "AND" by default
  • Explicit AND, OR, and NOT operators are supported for complex queries
  • Example queries:
    • group:sport HD matches channels in groups containing "sport" and with "HD" in their name (AND)
    • group:news OR group:weather (show channels in either group)
    • NOT 4K (excludes any channel with "4K")
• The UI should be forgiving: no operator = AND, explicit operator = honors the logic

Describe alternatives you've considered

• Relying on existing plain string filter (inefficient with large/complex channel sets)
• Advanced users manually managing their playlists instead

Additional context

• A filter bar help hint/popup or syntax cheat sheet would help adoption
• Consider a consistent filter syntax across EPG, playlist, and channel queries across the UI

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See also issue #1091 (related to improving normalization/filter flexibility) for consistent parsing of advanced filter tokens.